Feasibility of Heating Brain Tumors Using a 915 MHz Annular Phased-Array

Hyperthermia therapy and radiotherapy (RT) have been shown to increase the survival of brain tumor patients in randomized clinical studies using interstitial methods. To accommodate recent developments of external RT to treat brain cancer patients, we developed a noninvasive applicator to deliver localized heating to brain tumors. Using numerical simulations and phantom experiments, we demonstrated the feasibility of generating and steering a small heat focus of approximately 4 × 2 × 2 cm
³
in head phantoms. The heat focus was characterized using the SAR50 parameter, which is the 50% iso-volume of the normalized specific absorption rate (SAR). Multiple configurations were analyzed, including one, two, and three rings with 24 antennas each, as well 72-antenna applicators in a three-ring configuration controlled by 72, 24, and 8 amplifiers. The proposed design consists of a 915 MHz annular phased-array with 72 dipole antennas distributed in a three-ring configuration. Ongoing studies indicate the ability to group antennas so that only 8-24 amplifiers are required to make the antenna array construction feasible.